Category Car Chat

Today is the last day of April, from our website statistics below are the most popular articles of this month.

Transmission Titbit Series

Aisin 8AT
GM 8AT
ZF 9AT

Luxury Sedan AWD System Series

Part 1 – BMW xDrive, Mercedes-Benz 4Matic
Part 2 – Lexus, Audi Quattro

HongQi L-Series Luxury Sedan

Family Story – L5, L7, L9
L5 Model – V12 engine design, specificatioins

Aston Martin Financial Trouble

Aston Martin new car less than $100k
Why Aston Martin sell new car less than $100k
2012 financial analysis
2013 financial result and discussion

Last week I have discussed the GM 8AT and the ZF 9AT, today let’s take a look at the Aisin AA80E, which is used in the Lexus IS350, GS350, LS460, IS-F and the upcoming RC-F.

Unlike other longitude mounted 8AT such as the ZF 8HP and GM 8L90, the Aisin transmission uses compound planetary gear sets. A compound planetary gear set is a planetary gear set that has multiple sun gears or multiple ring gears. There are different types of them, the one we are interested in is called the Ravingeaux gear set, which has two sun gears, two planet carriers and they share one common ring gear.

One Ravingeaux gear set can provide 4 forward gear ratios and also the neutral and reverse.

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The torsional rigidity is a critical parameter for a vehicle, which measures how many force you need to apply to “twist” the car body frame by one degree. Of course the larger of this value, the better.

From the consumer’s perspective, what is the benefit of a high torsional rigidity car body? A vehicle with high torsion rigidity will give the driver and passenger a more “solid” feel when the car is running, especially when the road is bumpy and has lots of potholes on it...

Last time I showed you some interesting facts about the ZF 9HP transmission. Today I am going to talk about the latest GM 8L90 8-speed automatic transmission, which will be used on the 2015 Corvette.

Please do not be confused with the Cadillac CTS 3.6 V6 trim’s 8-speed transmission, that one is not the 8L90. Instead GM sourced it from Aisin and it is a completely different design.

First I would like to show you the structure diagram of the 8L90. The drawing is from the patent GM filed with the US Patent and Trademark Office several years ago. As expected in a patent document, the drawing looks terribly complicated...

The ZF 9HP is a 9-speed automatic transmission for transverse engine layout, which is used on the Jeep Cherokee and the upcoming Acura TLX. While there are plenty of technical analysis on this new ZF product, here I am not going to feed you with some PhD-thesis-type content. Instead I have some interesting facts you may find interesting.

First off, don’t be frightened by the below ZF 9HP internal structure image, it is for your reference only, you don’t try and memorize it all in one go. It takes time to learn.

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